Alternating wave generator



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TOPI/LSE' SELECM ajlolesrunggoun ia/0152@ mmf lNl/ENTOR H. W. AUGUSTADTALTERNATING WAVE GENERATOR Original Filed Sept.

curo-FF- a curar-F May 19, 1953 FIG.

ATTORNEY Patented May 19, 1953 UNITED PATENT sA'Liu`mi-m`irlIlG WAVEGENERATOR YHerbert 'W. "Augixstadt, Westfield, N.v kassignor ated;

k'7 Glaims.

l This is-a Vd-i-visiorfcftri-y prior 'applieton Serial No. "772,429,Iiled-:Septemberi 1947, for Aan im provement in indicating Apparatus,issued as Patent No. 2;546,814,Mar`c'h 2'?, 1951.

IThis invention relates to 'electrical Os'eillatory i potential of 'the'controllgrid leljeeinode in 'thev con- `meat-e branchtofa'relatively'lowne'gative value. Iny 'the l"manner that is Well in the art, thisnegativev potential "is vtiren removec'l` "from this controlY Agrid f'electrode' 'at 'an "exponential rate. When the control vgrid'potentialhas recovered, or risen, toa Av-a'luethat'is equalito'its 'c'u'teofivalue, current `'oen'izhrction again starts-'in that tube, which actiongives Lrise-to aother'success'ionof pulse'st-hat' result in'cuttingoi,or making non-'conductive the onjugatelhraneli;

If the' rising Control "grid: rpbtntiali's 'permitted 'to approacheut'i-eimvaluerat 'a gradual rate Aoi" cha-'nge ltherev'fill be 'a-Aco'risideraizlel portion of 'the 'oscillatory 'cycleduririg"Whi'charelatively small change 'in ciruitparareters; dr a relatively lsmallvoltage-impulseofthe-'proper pj'o'larityg may cause premature'reversal/oi theosei-llatorz This is true whetherftheescillater Visoperating as' ya free-running unit, or Whether it isbeing `op'f'erateclas Aa controlledyor driven riit. 1n 'this latter ease, of course, 'itisfnecessary' that thaunvvanted change or impulse-'occur' prior'ttlieco'ritroll-mg impulse that normal-1y' would" vcause'- theoseillators reversal. "It iskrevvriitiiat this vulnerable period-may bedecreased by` increasing theta-te of cha-ngeef theicontrel!gridpetentialduring the time it is'apm'o'aehing it'scut-'ofW-valua This,of course results'in'lthecotrl grid-poteritial beinginttre'neighborhoedof Vits cut-Uff" Valuefor'a, shorter time thandoesafrnerefgradual v change. f

Thispresent invention is.zireet'ed` tof-an vimprovedfmanner and meansfor seeuringincreased stability of operation' of relzmation oscillatorsvand particularly oscillators-fof the' multivibrator type by increasingthe rate Ofelia-nge of the grid charging nvoltage at. a* timevvcorrespon-trig to its cut-off value.

It is a1s`oanobjeet `ofthe invention'to improve the Yeertairday of:control-1 of relaxationfeseillators 'rn' accordance -wjith the presentinvention the staloility of Aio'seil 'tion fo'f thev i'fre'e-mnnimgoscillatr, or-tl're'ac'craeyi con'troliof the controlled, or tl-riven,"o 'illa'torarel greatly improved 'by-la 'novel "and tindtiv arrangementthat is 1empioy'e '1in the l`interetscites couplingv oir-cuits 'of me'oscillator.

This.l -novl and estimo ve arrangement operates to eifectively jgecre'ase 'the slope Y*of the-grid langifg vltage'i'duriirg its early"char-'ging period, andlto greatly increase the slope 1off thisv'h'argirg 'y'lta'ge -aV *period vlcorre'spending tbt'l're""cut'-oif"altre ofthe discharge device.

The v4reseiit; 'r1-tion will be readily unders'to'od from 4the'dllvvi-ng fietail'e'd description ""taken together the"ae'ceinpari-ying drawing, in which:

Fig.v -1 -is a AIcircuit diagramTof a multi-vibrator typefo relazatienlse 'tor Whieh'is Aconstrue-ted 'in-aeccyr'dancevvitlfi vv on; and

Figs. 2 and'S-fai'e ustrative' graphs to wh-ieh in Ldesoribirrgtheoperae K or `-1;

Fig'. "14 shows 'af--detal'el jsci-ierna-tie ef vva mul-tiVL 'vibratortypeof elaxatonoscillator which hm been'constret in ae rdanee-v'l'iththis iii-Veni tion. 2if-liefje mp'ii'ses a pair 0i lio'cle vaeumtu'jbesV8", each comijrising 'a' cathode, an anoeanw ontri eieotrode;Thannodeo'f tricfcie 'sico necterltothe oon-trolgri Eel-oftifiodefvt"thr ug cimeli-rig capacitor Cit, Whiohtogether h resistor Rafa,constitutes a diiferentiatin' network in the usual manner. The ranode ofrv'trioe -8' sjer'ineeftedte the een trol eieotrooeme or 1; eve throughAcrawling oai'acitor If'32e'arr"aegee in ajseriesresonant oir @uitvvvi'th resistor "Y'itan'iniictor L5. The lowerterininl lomeoilf-'Iriiis eo'rreetei to a vol-t afg'edivider'-eo This divi-de' 'for'Unt-meaidsiormak ing 'smalle Jus in thefree'erunningire- @identi-feite-o'sei-lljte'r. Cathode 5i of 'triele conne ted' te* grouse through avvvoltage dV-d-whi ids'l'sstr and RM, and theieathode'bf rioeVB 'iseenneetedte their umm-fion..` ycom;fisioLg doctor Le,y resistor' Essai-rcapacitors CM ane "C54v`v S ls nlllde'd4 the Cathode 4clvc'-tit OfftriodeVai This'aritiresonart 'circuit performs and these elements willnot be further considered in this description. For the purpose of thisexplanation it would be suiiicent if the cathode of triode V8 wereconnected directly to the upper terminal of resistor R44. Resistor R42is connected between control grid electrode B3 and the grounded terminalof voltage divider resistor R43. Positive voltage unidirectionalimpulses may be connected through capacitor C25 to the cathode end ofvoltage divider resistor R44 to control this multivibrator oscillator inthe manner will known in the art.

With the exception of capacitor C28 and inductor L5, all of thecomponents of the multivibrator may be chosen in accordance withwellknown design considerations. Capacitor C28 and inductor L5 form aseries resonant circuit, and in the optimum case are so chosen as to beresonant at a frequency slightly less than one-half of the desiredcontrolled oscillating frequency. In this described and testedembodiment values of .01 microfarad, .1 megohm and 26 henries were usedfor capacitor C28, resistor R38 and inductor L5, respectively. Althoughthese values do not exactly correspond to the previously describedoptimum relationship it was found that the addition of such a resonantcircuit imparted a marked degree of linearity to the grid chargingvoltage on electrode 43 as compared to the case where the resonantarrangement was omitted. As was previously stated, adjustment of thevoltage divider comprising resistors R39, R50 permits limited control ofthe free-running frequency of the oscillator.

The manner in which this circuit operates may be best understood fromthe following description. The introduction of positive voltage pulsesin the cathode circuit of one of the tubes, V8 or V8', While that tubeis conducting, gives rise to positive voltage pulses in the anodecircuit of the respective tube. These positive voltage pulses, Whenimpressed through coupling capacitors C28 and C29 upon the rising gridvoltage of the control electrode of the conjugate tube bring aboutreversal of the oscillator when the combined grid potential and pulsevoltage exceeds the cutoi voltage of the non-conducting tube. The gridvoltage graph of Fig. 2 indicates this condition for a conventionalmultivibrator which does not include the series resonant circuit of thisdescribed unit. Referring to this ligure, at time tl the voltage of onecontrol electrode has been driven negatively by the change in anodevoltage of the conjugate tube. This control electrode voltage increases,or rises, at an exponential rate that is largely determined by the RCvalue of the coupling capacitor and its associated grid leak resistor,and by the magnitude of the grid return voltage, such as is derived fromthe R39, RSU voltage divider. The value of this grid return voltage isindicated by the dotted line 16. At time t2, pulse 12 plus the increasedgrid voltage is suiiicient to raise the control electrode potential to avalue exceeding cut-off which is indicated by dotted line 14. At thistime current starts to flow in the previously cut off tube and quicklyreaches its saturated value. If no control voltage impulses, such aspulse 12, had been superimposed upon this rising grid voltage 10, thecoupling condenser would have continued to charge as an exponentialfunction, indicated by the dotted portion of curve 10, until the controlelectrode voltage had, at time t3, equalled the cut-off voltage 14 toinitiate current conduction in the tube. Because of the relatively slowrate of change of the rising grid voltage, as indicated by curve Tl),the peak potential on the control electrode caused by pulse 1l closelyapproximates that caused by the reversing pulse 12. It is apparent thatsmall changes in circuit parameters or pulse amplitudes during thiscritical period might cause premature circuit reversals. If the unit isoperated in a free-running or uncontrolled state the likelihood of someunstable condition causing a premature reversal before time t3 isaccordingly greater.

With the introduction of inductor L5 in series connection with thecoupling capacitor C28 and resistor R38, the rate of change in thevoltage on control electrode 43 is modied as is indicated by curve 8U ofFig. 3. When coupling capacitor C28 and inductor L5 are so proportionedas to be resonant at a frequency substantially less than thefree-running frequency of the oscillator, the rate oi' change of thevoltage on control electrode 43 is considerably decreased at a timeimmediately after time tl, and is considerably increased in the vicinityof the cut-off voltage of the tube, as indicated by dotted line v84.This condition is indicated by curve 8D, and the increased linearity ofthis grid charging voltage may be realized When curve is compared tocurve Hl of Fig. 2.

This improved rate of Voltage change is believed to be due to theself-inductive properties of inductor L5, by which it tends to opposeany change in the current flowing through the coil. At time tl (Fig. 3)corresponding to the start of conduction in triode V8', the potential oncontrol electrode 43 is driven negatively. Capacitor C28 immediatelystarts to equalize the voltage difference between its plates bydischarging through inductor L5, resistors R90, R3 8, R43 and R44, andthrough the space charge path of triode V8. At the start of thisdischarge period inductor L5 offers its maximum opposing electromotiveforce because of the high rate of change of current flow through it. Asthe discharging operation proceeds, the rate of change of current flowdecreases, and the opposing electromotive force offered by inductor L5also decreases. This force has its minimum value when the current flowreaches its maximum value. This permits a high rate of voltage increaseon control electrode 43 in the critical cut-off region. If theresistance R38 were completely removed, which it well may be, and ifpurely reactive components were available for use in place of capacitorC28 and inductor L5, the voltage on the control electrode 43 might risefrom its most negative value at time tl to its cut-off value 84 at timet2 in accordance with the theoretical cosine curve 18. Becauseresistanceless circuit components are not realizable, the theoreticalvoltage increase curve 18 is not actually achieved, but the linearizingef# fect of inductor L5 is realized, as is indicated by the solid linecurve 80. The degree of linearization that is actually realized in anyspecific instance may be increased or decreased by suitably changing thevalue of R38, even to the point of eliminating this component if it bedesired.

In Fig. 2 incoming pulse 'H immediately preceded pulse12, which pulsewould cause reversal of the oscillator. The corresponding situation isindicated for the oscillator of this invention by pulses 8| and 82 ofFig. 3. By inspection it will be noted that the linearized Voltageincrease, as indicated by curve 80, provides considerably more marginbetween the. maximum potential 8| and the cut-off potential 84 than isprovided between facscgeezs the *maximum potential Haii'dccutsoirpotential 14 of thesiconventionalfoscillator. .-,Inrthecase of the V controlled or driven joscillator this increased \marginVprovides added certaintyof synchronizaution,

When 1operating in a free-running state, vthe ,oscillator-of this"invention operates with, considerably improved "stabilityover'thatofi'the conventional multivibrator since; thefrate of change of thecontrol grid potentialds considerably in- -creased lover that o f theyconventionalx'nulti- 'v'ibra'tor. "This-meadows# thgccnrolleeifodevspotentially is 'in a vlnerablegposition, -orya :position in which" 'itmay be responsive to extraneous voltage impulses, for a shorter timethan in the case of the conventional unit. From the foregoing it will beseen that the increased rate of change in the control voltage tends tominimize the effect of power source fluctuations, or the effect ofextraneous voltage impulses.

Although this invention has been described in .connection With arelaxation oscillator of a specic type, and certain circuit componentvalues have been specifically enumerated, it should be realized that theinvention is not limited to this specic embodiment or to such componentvalues, since, modifications of the disclosed embodiment which arewithin the spirit and scope of the invention will undoubtedly occur tothose skilled in the art.

What is claimed is:

l. A multivibrator oscillatory circuit comprising two thermionicdischarge devices, each of said devices including an anode, a cathodeand a control grid electrode, anode-cathode and control grid-cathodecircuits therefor, the control grid of one oi said devices beingconnected to the anode of said other device through the capacitivemember of a resistance-capacitance time constant circuit, and thecontrol grid of said other device being connected to the anode of saidone device through'the capacitive member of a serially connectedinductance-capacitance circuit so proportioned as to resonate at afraction of the frequency of operation of said multivibrator oscillatorycircuit.

2. An alternating wave generator of the multivibrator type comprising apair of thermionic discharge devices, each having an anode, a cathode.and at least one control grid electrode, anodecathode and controlgrid-cathode circuits therefor, the control grid of a first of saiddischarge devices being connected to the anode-cathode circuit of thesecond of said devices through the capacitive element of a seriallyrconnected resistance-capacitance timing network, the control gridelectrode of said second device being connected to the anode-cathodecircuit of said rst device through the capacitive member of a seriallyarranged inductive-capacitive circuit, said circuit elements beingproportioned to resonate at a frequency substantially equal to one-halfof the frequency of operation of said alternating Wave generator, andsaid inductive element being included in the control grid-cathodecircuit of said second device. c

3. An oscillation generator comprising a pair of thermionic dischargetubes, each comprising an anode, a cathode and a control grid electrode,an anode load resistor connected to each anode and a source of positivepotential connected to each anode load resistor, a coupling capacitorconnected between the anode and the control electrode respectively of afirst and second of said -6cdischargeftubes,arresistoriconnectedfin@thefcon-.'@trolfxelectrodeecathodescircuiti-offsaidsecond'dis- Acifrar-griftube, .a f second coupling .capacitor connectedbetweentthe,anode ofi.said second. tube; and ithefcontrolaelectrode-ofesaidiiirststubesandcanindoctorserially,connectediwithsaidfsecondvcapacittor: and-'includedinfrthecontrohelectrode-cathode :circuitf of said Ai'irst .'tube,iinductorsand .said :secondr coupling leapacitoipbeinguso :arrangedas toAforma'seriescircuit withtheirvalues chosen such f that :said: elements:resonate .at -a .firequencwbeytweenfone-fourthfarrdathree-fourthsz.birthe operating-Ifrequencyoisaid: oscillationtgenerator.

...14.'1An-.oscillationa-generatorlcomprising a-.zpa-ir.vv of"therm'ioriicdischargetubesg each.' comprising an anode, a cathode and acontrol;gridaelectrodefan anodeiload"resistor'connectedito each anodeand a source of positive potential connected to each anode through saidload resistor, a coupling capacitor connected between the anode and thecontrol electrode respectively of a first and second of said dischargetubes, a resistor connected in the control electrode-cathode circuit ofsaid second discharge tube, a second coupling capacitor connectedbetween the anode and the control electrode respectively of said secondand first discharge tubes and an inductor serially connected with saidsecond capacitor and included in the control grid-cathode circuit ofsaid second discharge tube, said inductor and said second couplingcapacitor being of such sizes that they present opposed impedances ofsubstantially the same magnitudes at a frequency equal to about one-halfthe frequency of oscillation of said oscillation generator.

5. An oscillation generator comprising a pair of thermionic dischargetubes, each comprising an anode, a cathode and a control grid electrode,a source of positive potential connected to each anode through anindividual anode load resistor, a coupling capacitor connected betweenthe anode and the control electrode respectively of a rst and second ofsaid discharge tubes, a resistor one end of which is connected tol saidcoupling capacitor and to the control electrode of said second discharge`tube, a voltage dividing resistance network having two outer terminalsand an intermediate terminal, one of said outer terminals beingconnected to the cathode of said second discharge tube, the other ofsaid outer terminalsl beingA connected to said control grid resistor,the cathode of said rst discharge device being connected to theintermediate terminal of said resistance network, a second couplingcapacitor connected between the anode of said second discharge tube andthe control electrode of said rst discharge tube, a series circuitcomprising `a resistor and an inductor, said resistor being connected tosaid second cap-acitor and to the control electrode of said firstdischarge tube and said inductor being connected to said voltagedividing resistance network, the magnitudes of said inductor andcapacitor being so chosen that they present substantially a resistiveimpedance at a frequency equal to one-half the oscillating frequency ofsaid generator.

6. An oscillation generator comprising a first and seco-nd electro-ndischarge device each including a cathode an anode and a control gridelectrode, a load resistor connected to each anode, means including saidresistors to maintain said anodes at a potential positive With respectt0l said cathodes, a capacitor and a resistor connected in seriesbetween the anode and cathode electrodes of said first device, acapacitor and an indu'ctor connected in series between the anode andcathode electrodes of said second device, a direct connection betweenthe control electrode of said rst device and the junction of saidcapacitor and inductor, a direct connection between the controlelectrode of said second device and the junction of said capacitor andresistor. said series-connected capacitor and inductor being o-f suchmagnitudes as to resonate at a fraction of the frequency of oscillationof said devices.

7. An oscillation generator in accordance with the preceding claimwherein said series-connected capacitor and inducto-r are soproportioned that they are resonant at a frequency slightly less thanone-half the oscillation frequency of said devices.

HERBERT W. AUGUSTADT.

References Cited in the le of this patent UNITED STATES PATENTS NumberNumber Name Date Braaten Feb. 16, 1937 Gottier Apr. 29, 1947 Grieg et alAug. 26, 1947 Harris Aug. y1, 1950 FOREIGN PATENTS Country Date GreatBritain Sept. 6, 1934 Great Britain Aug. 25, 1936 Great Britain Jan. 3,1947

